Apparatus and methods for generating persistent ionization plasmas

Abstract

A persistent ionization plasma generator is described that forms a plasma in a cavity that persists for a time after termination of the exciting RF electric field. The plasma generator includes a RF cavity that is in fluid communication with a source of ionizing gas. The RF cavity can be at substantially atmospheric pressure. An RF power source that generates an RF electric field is electromagnetically coupled to the RF cavity. An ultraviolet light source is positioned in optical communication to the cavity. An antenna is positioned within the cavity adjacent to the ultraviolet light source. A chamber for confining the plasma can be positioned in the cavity around the antenna.

1. A method for reducing aerodynamic drag of an aircraft, the method comprising:
 positioning an antenna on a surface of an aircraft;  
 electromagnetically coupling a RF electric field to the surface of the aircraft proximate to the antenna;  
 optically coupling ultraviolet radiation to the surface of the aircraft proximate to the antenna, thereby causing ignition of a plasma; and  
 terminating the RF electric field, thereby generating a plasma that persists for a time after termination of the RF electric field, and reducing aerodynamic drag on the surface of the aircraft.  
 
   
   
     2. The method of  claim 1  wherein optically coupling the ultraviolet radiation comprises optically coupling ultraviolet radiation produced by a spark plug to the surface of the aircraft. 
   
   
     3. The method of  claim 1  wherein optically coupling the ultraviolet radiation comprises optically coupling ultraviolet radiation produced by a laser to the surface of the aircraft. 
   
   
     4. The method of  claim 1  wherein the RE electric field has a frequency of 2.45 GHz. 
   
   
     5. The method of  claim 1  wherein the RF electric field has a frequency of 915 MHz. 
   
   
     6. The method of  claim 1  wherein the time after termination is greater than about 1 ms. 
   
   
     7. The method of  claim 1  further comprising the step of operating the aircraft. 
   
   
     8. The method of  claim 7  wherein the step of operating the aircraft comprises operating the aircraft in a transonic regime. 
   
   
     9. The method of  claim 7  wherein the step of operating the aircraft comprises operating the aircraft in a supersonic regime. 
   
   
     10. The method of  claim 7  wherein the step of operating the aircraft comprises operating the aircraft in a hypersonic regime. 
   
   
     11. A system for reducing aerodynamic drag on an object, comprising:
 an antenna positioned on a surface of an object;  
 an RF generator in electrical communication with the antenna, the RF generator producing an RF electric field that electromagnetically couples to the surface of the object proximate to the antenna; and  
 an ultraviolet radiation source that optically couples ultraviolet radiation to the surface of the object proximate to the antenna, thereby causing ignition of a plasma;  
 whereby the plasma persists for a time after termination of the RF electric field, reducing aerodynamic drag on the surface of the object.  
 
   
   
     12. The system of  claim 11  wherein the ultraviolet radiation source comprises a spark plug. 
   
   
     13. The system of  claim 11  wherein the ultraviolet radiation source comprises a laser. 
   
   
     14. The system of  claim 11  wherein the RF generator is adapted to operate at a frequency of 2.45 GHz. 
   
   
     15. The system of  claim 11  wherein the RF generator is adapted to operate at a frequency of 915 MHz. 
   
   
     16. The system of  claim 11  wherein the persistence time after termination is greater than about 1 ms. 
   
   
     17. The system of  claim 11  wherein the object is an aircraft having a surface. 
   
   
     18. The system of  claim 17  wherein the aircraft is adapted to operate in a transonic regime. 
   
   
     19. The system of  claim 17  wherein the aircraft is adapted to operate in a supersonic regime. 
   
   
     20. The system of  claim 17  wherein the aircraft is adapted to operate in a hypersonic regime.